These studies are directed towards elucidating the molecular basis of glycogen synthase activity in liver. For the most part the study of the control of glycogen metabolism has focused on the interconversion enzymes. However, it is likely that molecular modification of the enzyme substrates also has a role. For example, microheterogeneity in synthase I kinase and synthase D phosphate. We have preliminary evidence that synthase D exists in different forms in normal fed, diabetic fed and adrenalectomized fasted animals. Synthase D, synthase I and possible intermediate forms will be isolated from various animal preparations. A correlation will be made between the phosphorylation states, kinetic properties and suitability as substrates for the interconverting enzymes. A purified liver synthase D has been reported to contain 12 phosphates per subunit. The number of phosphates in synthase I has not been determined. Antibodies to synthase will be used in some of the above studies. In addition, protein-protein interaction of purified synthase with the various proteins involved in its regulation will be investigated and the importance of interaction estimated using a "leaky" cell preparation. These studies are important to the understanding of how complex enzymes control crucial steps in the glycogen metabolic pathway.